Deviometers, as is known, make it possible to ensure a double function: the detection of a laser spot and the tracking of said spot. To this end, the deviometers of the prior art proceed in two phases:                initially, they ensure the detection of laser flashes, and the identification of the emission code for the associated laser spot, corresponding to a measurement of the instants of emission of the laser at the origin of the spot;        subsequently, they ensure the measurement of the position of the laser spot on a detector with four quadrants, by means of servocontrol aimed at centering the laser spot on said four-quadrant detector.        
The main defects of these known deviometers are the following:                they exhibit a conflict between the size of the observed field and the sensitivity of the device: the more the observed field increases, the more considerable the noise and the more reduced the sensitivity;        the precision of measurement of the position of a laser spot on a four-quadrant detector is today insufficient in relation to needs.        
To significantly improve the performance of these deviometers, notably in terms of precision and sensitivity, it turns out to be necessary a priori to develop fully matrix technologies.
The main solutions proposed are described in patents US 2003/0209650 and US 2003/0205663.
In the case of patent US 2003/0209650, there is disclosed a scheme consisting of the construction of a small reconfigurable matrix making it possible to displace a four-quadrant detector in a field of large dimension. A small reconfigurable matrix of photodiodes such as this allows fast detection of the position of the laser spot. This positioning is done by an iterative reduction in the field of vision so as to converge toward the precise position of the laser spot on the matrix of photodiodes.
In patent US 2003/0205663, there is described a deviometer comprising a readout circuit exhibiting a matrix of “intelligent” pixels, in the sense that said “intelligent” pixels themselves ensure the role of so many independent detectors, having their own inherent electronics. The “intelligent” pixels have the capacity to store the detected laser pulse. Thereafter, a global “OR” is applied to the set of pixels, allowing precise determination of the position of the laser spot on the matrix.
The known laser spot detectors exhibit various drawbacks, as a function of the technology that they implement. Four-quadrant detectors, though they are fast and allow continuous surveillance, have a sensitivity which decreases rapidly with the size of the observed field. Matrix solutions exhibit the defect of requiring complex, and therefore expensive electronics, in particular as regards the “intelligent” pixels. Moreover, “intelligent pixels” such as these, on account of their complexity, necessarily exhibit considerable dimensions, greater than 50 μm, entailing limited measurement precision. Furthermore, the electronics hampers the photodiodes and causes the loss of numerous photons.
Finally, the known matrix deviometer technologies require continuous reading of the set of pixels, over a potentially long integration time, so as to detect the arrival of a laser pulse. Long integration times such as these cause considerable noise, and therefore reduced sensitivity of the detector.